Numerous oxazolidinone compounds have been reported having therapeutically and/or prophylactically useful antibiotic or antimicrobial, in particular antibacterial, effect. Among such compounds are those illustratively disclosed in the following patents, each of which is individually incorporated herein by reference.
U.S. Pat. No. 5,164,510 to Brickner.
U.S. Pat. No. 5,231,188 to Brickner.
U.S. Pat. No. 5,565,571 to Barbachyn & Brickner.
U.S. Pat. No. 5,627,181 to Riedl et al.
U.S. Pat. No. 5,652,238 to Barbachyn et al.
U.S. Pat. No. 5,688,792 to Barbachyn et al.
U.S. Pat. No. 5,698,574 to Riedl et al.
U.S. Pat. No. 6,069,145 to Betts.
Compounds disclosed in above-cited U.S. Pat. No. 5,688,792 include for example the compound (S)-N-[[3-[3-fluoro-4-(4-morpholinyl)phenyl]-2-oxo-5-oxazolidinyl]methyl]acetamide, also referred to herein as linezolid. Linezolid has the structure shown in formula (I): and is in commercial use as a medicament under the trademark Zyvox® of Pharmacia Corporation. Linezolid exhibits strong antibacterial activity against gram-positive organisms including those of the following genera: Staphylococcus (e.g., Staphylococcus aureus, Staphylococcus epidermis), Streptococcus (e.g., Streptococcus viridans, Streptococcus pneumoniae), Enterococcus (e.g., Enterococcus fecalis, Enterococcus faecium), Bacillus, Corynebacterium, Chlamydia and Neisseria. Many such gram-positive organisms have developed significant levels of resistance to other antibiotics. Oxazolidinone antibiotics are also generally effective against anaerobic organisms such as those of the genera Bacteroides and Clostridia, and against acid-fast organisms such as those of the genus Mycobacterium. 
Above-cited U.S. Pat. No. 5,688,792 discloses that the subject antibiotic oxazolidinone compounds, including linezolid, can be formulated as liquid form compositions including solutions. For example, it is disclosed therein that a solution can be provided of a subject oxazolidinone compound in water or in a water-propylene glycol or water-polyethylene glycol system, optionally containing conventional coloring agents, flavoring agents, stabilizers and thickening agents.
It is further disclosed in above-cited U.S. Pat. No. 5,688,792 that the subject oxazolidinone compounds can be administered orally, parenterally and/or topically, and that parenteral administration can be by intravenous injection or other parenteral route. For parenteral administration, it is disclosed therein that a suitable composition will generally contain a pharmaceutically acceptable amount of a subject oxazolidinone compound as a soluble salt dissolved in a liquid carrier such as water for injection to form a suitably buffered isotonic solution. Such a solution is stated therein generally to contain a subject oxazolidinone compound dissolved in the carrier in an amount sufficient to provide an injectable concentration of about 1 to about 400 mg/ml of solution.
Many oxazolidinone compounds useful as antibiotics do not form, or do not readily form, salts. For these compounds, and where for any reason it is preferred not to provide the antibiotic in salt form, it is generally difficult to formulate the antibiotic as a solution in a pharmaceutically acceptable liquid carrier, particularly an aqueous carrier. Most such compounds have relatively low solubility in water; in the case of linezolid, for example, the solubility at ambient temperature is less than 3 mg/ml and the practical limit of concentration in aqueous solution is about 2 mg/ml.
Particularly where parenteral or oral administration of an oxazolidinone antibiotic drug is contemplated, it is desired to achieve systemic concentrations of the drug in the bloodstream above a minimum inhibitory concentration for 90% of target organisms (MIC90). It will readily be understood that it is difficult to achieve such concentrations by administration of a relatively small volume of a composition wherein the drug is present in dissolved form, unless the composition has a relatively high drug loading, and in particular a drug loading substantially above the limit of solubility in water of most oxazolidinone antibiotics not in the form of a salt.
A need therefore exists for a solution composition of an oxazolidinone antibiotic drug having a drug loading substantially in excess of the practical limit of solubility of the drug in water. A particular need exists for a parenterally deliverable solution composition of an oxazolidinone antibiotic drug having a relatively high concentration of the drug.
These and other needs will be seen to be met by the invention now described.